The vulnerability exists in GitPython's Repo.init() method, which forwards all keyword arguments directly to the underlying git init command without any guard against unsafe options. The --template option allows specifying a directory whose hooks are copied into the new repository's .git/hooks directory. An attacker who can control the template directory can plant malicious hooks that execute arbitrary code on the next git operation. Unlike git clone, which has a denylist for unsafe options, Repo.init() lacks such checks, making it vulnerable. The attack requires two conditions: the application must forward a template kwarg controlled by the attacker, and the attacker must stage an executable hook directory at a known path. This vulnerability is tracked as GHSA-9rj7-rf2p-w77r and affects GitPython versions prior to 3.1.58.

Successful exploitation results in arbitrary code execution with the privileges of the host process running the git operation. The attack complexity is high because the attacker must both stage an executable hook directory and influence the template argument passed to Repo.init(). The impact includes full compromise of the affected environment through malicious git hooks triggered on subsequent git commands.

A patch is available that adds a check_unsafe_options guard to Repo.init(), including a denylist of unsafe options such as --template and --separate-git-dir. Users should upgrade to GitPython version 3.1.58 or later where this fix is implemented. Until patched, avoid passing untrusted input to the template parameter in Repo.init() to prevent arbitrary code execution.